Method of deaeration



July 3, 1934. J, R MCDERMET 1,965,386

METHOD OF DEAERATI ON Filed Jan. 28, 1932 Q%NTOR I Patented July 3, 1934 METHOD OF DEAERATIQN John R. McDermet, .l'e

Elliott Company of Pennsylvania Application January 28 2 Claims.

The present invention relates broadly to the art of deaeration, and more particularly to an improved method eifective for the removal of air from water for the purpose of rendering avail- 5 able a continuous supply of deaerated water such as to satisfy the demands for example of a modern power plant or the like.

In the deaeration process, there are certain conditions which must be initially obtained and thereafter continuously maintained in order to insure the production of deaerated water within the commercially accepted sense. In accordance with certain known processes, it is customary to provide distinct stages of treatment through which the water passes successively during the deaerating process. The present invention relates more specifically to a multiple treatment zone apparatus and method of this general character.

In such apparatus, the water is usually brought into contact with heating steam in one of the zones' which, by reason of its primary provision {or heating purposes may be referred to as the heating stage. In this stage the water is raised 'to a temperature substantially as high as it is possible to raise it in the presence of air in the steam originally supplied for heating purposes plus the air released from the water during the heating operation, it being understood thatthe solubility of air in water is a function of the temperature and that the solubility decreases as the temperature increases. It is well recognized that this temperature differential between the full steam temperature of the supplied steam, and 3 the water undergoing treatment, is such that 5 there is a considerable air content left in the water. This air content is subsequently removed by subjecting the water to treatment in a second stage provided primarily for the purpose of effecting complete or substantially complete air 40 elimination; and therefore commonly referred as a deaerating or pressure stage.

The term pressure stagev is significant in that in this stage the partial air pressure in the steam atmosphere is maintained so low that the air in the water passes out of the water in an attempt to establish a pressure equilibrium between the air content of the water and the air content of the ambient steam atmosphere. This pressure equality is in accordance with the law 0 of Henry to the effect that gases, including air and its constituents, dissolve in water inproportion to their partial pressures at the surface of the water or in contact therewith.

In the two stage or two zone treatment heretofore provided, it has been customary to provide annette, Pa., assigner to Jeannette, Pa, a corporation 1932, Serial No. 589,368 (Cl.'183--2.5)

a thoroughfare type of steam heater cons tituting the pressure sta ge, and an induction -type of heater constituting the heating stage. the heating steam passing first through the thoroughfare heater and thence into the induction heater, with the water passing in the reverse direction, i. e., first through the heating stage and thence into and through the deaerating' stage. In this manher, water previously heated in the heating stage is subjected to the substantiall mosphere initially admitted to the pressure stage.

It is, however, open to the objectionihat all of the air from the pressure stage as well as the air released in the heating stage, are in more or less intimate contact with the water in the heating stage. In this stage the water being admitted contacts with this air-rich atmosphere in such manner that reabsorption. of'a considerable portion of theair is made possible. [Whie this air is again released during the heating operation, it becomes apparent that the operation of the apparatus is' inherently such as to require a re-handling of a 'considerableportion of the air content. I I

It is one of the objects of the present invention to provide a two stage or two zone type of water treatment wherein the waterand steam instead of flowing counter one to the otheig fle w generally in the same direction in such manner that air once relc 158d from the water undergoing treatment is at no time permitted to com tact with water at a temperature or under conditions such that reabsorption of the air is permitted. T

In accordance with the present invention the water is subjected to successive treatments in diiierent stages or zones. Each such zone provides a series of steam strata through which the water passes progressively, thus insuring a progressive increase in water temperature as the water passes from stratum to stratum in either stage. In order, however, to obtain the most y pure steam atbeneficial results, it is desirable that the various strata be subjected to a steam withdrawal action, at least in the pressure stage, of such character that the stratum having the least temperature rise is subjected to the mostefiective withdrawal. v o M By way of general introduction, it may be-assumed that in an apparatus of the tray-type,

the water is to pass successively overeach of the desired number of trays. These trays will ob viously define horizontally superimposed zones or strata through which the water progressively passes in going from one tray to the other. As

each of the strata is supplied with heating steam, the temperature rise in the first stratum will be greater since in this zone the coldest water comes into contact with the steam Thereafter, the temperature rise will be a more gradual one, which may be considered as generally comparable to the time element together with the rate of air removal. Thus, in the last stratum of treatment the temperature rise will be of a minimum amount and, except for affording a possibility of pressure equilibrium of the character referred to, almost negligible.

Since, however, pressure equilibrium involves by its very nature the'release of air from the water, and therefore air'contamination of the steam atmosphere, it is essential that the steam atmosphere be continuously renewed. Since the temperature rise, as before stated, is almost negligible in -the last stratum of treatment, thetendency toward any induced flow of steam into such stratum is likewise almost negligible. Under normal conditions of operation, there is a possibility of 'air stagnation in each stratum. It is one of the objects of the present invention to provide a method and apparatus characterized by the possibility of effecting continuous renewal of the steam atmosphere in such stratum by insuring a continuous passage of steam thereinto and its continuous removal therefrom.

Since, as before pointed out, the temperature rise in the successive strata is a decreasing one, the steam flow induced. in such strata is likewise a decreasing one. It. is further one of the objects of the invention to provide a method and apparatus characterized by the possibility of modifying the normal steam flow into such strata and establishing and. continuously maintaining conditions such that the tendency toward steam flow into the various strata is progressively. increased in the direction of water flow. f In accordance with the present invention, such a result may be accomplished. by making provision for a more effective venting. of the strata progressively "in the direction "of water fiow twhereby .thelast. stratum is characterized .by a greater ipotential nventing capacity than ,the stratum preceding. it, the capacity preferably depia'singegradually in a direction counter tothe lwaterl flow, zzalthoughe-any, provision, 91;, disposiltionr ofimartsswhereby ,qthe desired preferential the ipresentwinventlonme so-rlteis ot-courseepos 'accomplishingegstea ,movementirthrough an apparatus,;,or;.-tovsupplyesteam under appreciable pressure-and vent it in'large quantities directly to the atmosphere. Both of these methods, however, are open to the objection that the heat of the steamthus'withdrawnis lost. In accordence. with':the,,present invention, I preferably utilize a withdrawing or steamflow inducing means of suchnature that it is possible to continuously recoventhe heat of withdrawn vapors and gases and, impart the sameto an appreciable extent'to-the water to be-deaerated. a

For thispurpose-I preferably utilize-fa W0 Surracetype vent condenserysuch apiece of equipment being characterized, by ability to withdraw vapors andgases. and induce thedesired flow gpnditions, andibytheability .to transfer alarge lilac-ta; utiliaeei t s lgreferably utilize geaeratdasthe condensing-"medium.

gum .a v t'condenser The accompanyingfigure of the drawing, which is largely diagrammatic, illustrates one form of apparatus by means of which the present invention may be practiced. In accordance with this iagrammatic showing there is provided a suitable casing 2 having a water inlet 3 leading into its upper portion. Disposed within the 'water inlet is a float operated valve 4 operatively co nected to a float 5 disposed in the water storage space 6 in the bottom portion of the apparatus and therefore having its position determined entirely by the water level therein. Leading from the water storage space is an outlet 7 for the purpose of conveying deaerated water to the point of ultimate use. The position of the float is thus responsive to demands on the apparatus and the supply of water is correspondingly ,automatically controlled in accordance with the load.

Leading into one side of the apparatus adjacent the upper portion thereof is a steam inlet 8 communicating with a heating zone H. Within this zone is a series of conventional trays 9 such as customarily provided in water heaters of the open type. The admitted steam passes between the trays as indicated by the arrows 10 in the form of superimposed strata, leaving the same and passing downwardly as indicated generally by the arrows 11. 1

It is a desirability of the present invention that the heating zone H be characterized by its ability to accomplish the desired heating of the supplied water at an extremely rapid rate under favorable conditions of maximum temperature gradient, high steam velocities and the like. Its value resides substantially completely in its spaceor weight efficiency and its commercial inexpensiveness. In this heating compartment the water admitted to the apparatusis subjected in-broken up condition to the action of the admitted steam in such manner that the temperature of the-water is rapidly raised, thus efiecting airelimination. This eliminated air together. with the steam not condensedin the heating, duty,-.pass

into the pressure zone Pin the manner before referred to, Within this. zone there are .placed in superimposed relationship trays 12 .whichagain divide the steam .iiow into a pluralityof super-e imposed strata, the strata leaving the trays as indicated by the arrows 14 and flowing downwardly as a solid stream through a spac e 15 and partition By reference to the drawing it will be noted that the outlet spaces 1'7 from ,the .successive trays. progressively increase. in siz'elin a direction downwardly. of fth'eftray. stacker-Yin the direction between thewater andthe combinedbottom tray tom trayf being. of maximum size increase in ai'r'te'i'ision inaybeeffectively counter acted by supplying a' greater heat quantity iii-"th form of excessive steam, and by providing a slightly larger-tray area than. ordinarily" considered necessar eneess lheatf quantity 40 vent condenser for cooling purposes, therefore, is in air may be removed comparatively easily has 115 must in turn be removed from the apparatus and apparatus so as to insure such an air-steam ratio the heat thereof conserved. in the pressure zone P that the partial air pres- For this purpose, I connect the space 15 to sure due to the air in the air-steam mixture in the vapor inlet 18 of a vent condenser 19 and this zone will be below the partial pressure of cause the air-steam mixture to pass in itimate air in the water to be delivered from the appara- 80 contact with the condenser tubes 20 through tus. This desired air-steam ratio is continuously which the water flows from an inlet 21 to an maintained by excessive venting, the vent conoutlet 22, the outlet 22 being suitably connected denser being designed to handle the necessary to the inlet 3 as indicated in the drawing. The steam quantity to accomplish this object.

0 condenser is provided with the usual vent 23 In abstracting heat from the vapor mixture, 85

either permitting the uncondensable content of the vapors are necessarily condensed in the conthe mixture to discharge directly to the atmosdenser, thereby decreasing the volume and tendphere, or provided with an ejector or air pump ing to create a vacuum, this tendency being efas operating conditions dictate. fective-through the connection 18 for withdraw- With an apparatus of the character referred ing further vapors from the apparatus into the 90 to, the vent condenser is made considerably condenser. The condenser thus constitutes a larger than vent condensers as customarily detrue withdrawal means, the effectiveness of which signed for water handling apparatus of the same on the respective strata is determined by the size, whereby excessive venting and therefore exsize of the respective openings 17. By reason of cessive steam flow is constantly insured. Inasthe gradual increase in size of these openings in 96 much as the heat of the vented mixture is imthe direction of water flow, it is obvious that the parted to the water to be deaerated, the operatcondenser has the ability to exert a greater pull ing cost of the apparatus is not so increased as on the bottom stratum than it has on the top to detract appreciably from its commercial use. stratum in the zone P, the effectiveness of the 25 The vent condenser is thus initially proporpull increasing progressively in the direction of 100 "tioned to maintain enough .condensing capacity water flow. to provide a deaerating atmosphere in the lower Since the water temperature gradually incompartment. The necessary size of the vent creases in passing over the successive trays, its condenser is calculated upon the basis of the air content progressively decreases, the air conmaximum load, keeping in mind the established tent being at a minimum adjacent the bottom 105 temperature conditions. In actual practice, tray. The curve representingair removal is of these conditions remain constant but the load as the character ordinarily referred to as an measured by the quantity of water treated, varies. asymptotic curve and illustrates the difficulty It is to be noted that the quantity of water under natural conditions of operation of effecting passing through the vent condenser as cooling complete air removal, the last quantity of air be- 110 fluid subsequently reappears with the slight addiing removed only with considerably greater diftion of the condensed heating steam, in the ficulty than the initial portions.

' deaerating compartment, as the quantity of In accordance with applicant's invention, the

water being deaerated. The circulation of the upper steam stratum in the pressure zone wherecontinuously in exact proportion to the quantity a smaller steam flow than the bottom stratum, of water being treated, except for the slight conwherein air is removed with greater difliculty. densate resulting from the heating steam. This The maximum steam flow from the stratum for ratio of steam removed and condensed to the the minimum air content insures the continuous total quantity of water being handled thus remaintenance of an air-steam ratio in this stratum 120 mains constant, as will be obvious from a consuch that the desired pressure equilibrium may sideration of the fact that the vent condenser be advantageously accomplished. cooling water circuit is in series with the deaerat- While I have herein illustrated and described ing circuit or, in other words, the water to be strata of treatment of the type formed by superdeaerated passes through the vent condenser to imposed trays, it will be understood that such 125 condense any steam remaining uncondensed strata may be otherwise formed, and that the therein before passing to the heating anddeisolation or separation of the respective strata aerating chambers. may be modified or changed in accordance with The direction of the steam and water flow is the particular design of the apparatus.

such that the released air is concentrated down- I claim: 1

wardly through the apparatus toward the water 1. A method of deaerating water including the storage space. The water in this space has been steps of delivering the water to a chamber, supheated to the highest temperature possible by plying steam to the chamber to effect rapid heat the apparatus, and therefore represents a region ing and partial deaeration of the water, passing where the solubility of air in the water is at a the partially heated water, the air released thereminimum. By sweeping the venting steam across from, and any uncondensed steam to a second the water surface, any accumulated air is conchamber for further heat exchange, continuing tinuously removed, the point of air removal being the supply of steam through said first-mentioned from a region wherein the solubility of air in the chamber in an amount sufficient to maintain in water is at a minimum and therefore overcoming the second chamber an atmosphere favorable to the objections to forms of apparatus wherein the further absorption of air from the water therein, air is permitted p upwardly in the pp e withdrawing air and steam from the successive direction as necessitated by a counter current ortions of the second chamber in amounts insteam flow, and thereby into contact with the creasing progressively in the direction of water 7 water where air solubility is at a max mumflow through said second chamber, and condens Knowing the initial air content of the water ing any steam leaving the second chamber t to be deaerated, and knowing the extent to which at a, pressure difference sufiicient to maintain air remova is to be effected, it is possible 120 continued flow of steam through said chambers termine what the partial air pressure of the rein the amounts aforesaid, v

75 maining air inthe water will be and to design the 2. In a, method of deaerating a liquid, the steps 1 tions of the second chamber in amounts increasing progressively in the direction of the fiow of liquid therethrough, and finally removing from the second chamber and condensing any previously uncondensed vapor therein, and controlling the quantity of vapor so finally condensed to maintain conditions in the second chamber favorable to continued deaeration.

JOHN R. McI JERMET. 

